<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // let str = '123'
        // console.log(Number(str))
        // // let num = prompt('请输入一个数字')
        // // console.log(typeof Number(num))
        // let num = Number(prompt('请输入一个数字'))
        // let num1 = +prompt('请输入一个数字')
        
    </script>
</body>
</html>